diff --git a/src/models/entities/DistanceDonation.ts b/src/models/entities/DistanceDonation.ts
index 669f88f..d5610d7 100644
--- a/src/models/entities/DistanceDonation.ts
+++ b/src/models/entities/DistanceDonation.ts
@@ -29,10 +29,17 @@ export class DistanceDonation extends Donation {
    * The exact implementation may differ for each type of donation.
    */
   @IsInt()
-  public get amount(): number {
+  public get amount() {
+    return this.getAmount();
+  }
+
+  /**
+   * The function that calculates the amount based on the runner object's distance.
+   */
+  public async getAmount(): Promise<number> {
     let calculatedAmount = -1;
     try {
-      calculatedAmount = this.amountPerDistance * this.runner.distance;
+      calculatedAmount = this.amountPerDistance * await this.runner.distance();
     } catch (error) {
       throw error;
     }
diff --git a/src/models/entities/Donation.ts b/src/models/entities/Donation.ts
index c4ab699..2609a98 100644
--- a/src/models/entities/Donation.ts
+++ b/src/models/entities/Donation.ts
@@ -1,10 +1,9 @@
-import { PrimaryGeneratedColumn, Column, ManyToOne, Entity, TableInheritance } from "typeorm";
 import {
   IsInt,
   IsNotEmpty,
-  IsOptional,
-  IsPositive,
+  IsOptional
 } from "class-validator";
+import { Entity, ManyToOne, PrimaryGeneratedColumn, TableInheritance } from "typeorm";
 import { Participant } from "./Participant";
 
 /**
@@ -32,5 +31,5 @@ export abstract class Donation {
    * The donation's amount in cents (or whatever your currency's smallest unit is.).
    * The exact implementation may differ for each type of donation.
    */
-  abstract amount: number;
+  abstract amount: number | Promise<number>;
 }
\ No newline at end of file
diff --git a/src/models/entities/Runner.ts b/src/models/entities/Runner.ts
index 2496d98..7a8d0ad 100644
--- a/src/models/entities/Runner.ts
+++ b/src/models/entities/Runner.ts
@@ -54,7 +54,7 @@ export class Runner extends Participant {
    * Returns the total distance ran by this runner.
   */
   @IsInt()
-  public get distance(): number {
-    return 0;
+  public async distance(): Promise<number> {
+    return await (await this.getValidScans()).reduce((sum, current) => sum + current.distance, 0);
   }
 }
\ No newline at end of file
diff --git a/src/models/responses/ResponseRunner.ts b/src/models/responses/ResponseRunner.ts
index 677ca93..01327c2 100644
--- a/src/models/responses/ResponseRunner.ts
+++ b/src/models/responses/ResponseRunner.ts
@@ -26,7 +26,7 @@ export class ResponseRunner extends ResponseParticipant {
 
     public constructor(runner: Runner) {
         super(runner);
-        this.distance = runner.scans.reduce((sum, current) => sum + current.distance, 0);
+        this.distance = runner.scans.filter(scan => { scan.valid === true }).reduce((sum, current) => sum + current.distance, 0);
         this.group = runner.group;
     }
 }