Lendable Interview Test - Fee Calculation

Implement FeeCalculatorInterface such that it fulfills the fee structure below. The fee structure does not follow a formula.

Values in between the breakpoints should be interpolated linearly between the lower bound and upper bound that they fall between. The fee should then be "rounded up" such that (fee + loan amount) is an exact multiple of 5.

The minimum amount for a loan is £1,000, and the maximum is £20,000. You can assume values will always be within this range but they may be any value up to 2 decimal places. The term can be either 12 or 24 (number of months), you can also assume values will always be within this set.

Provide a test suite verifying your solution, use any testing framework you feel comfortable with. Use any libraries (or none) you feel add value to your solution.

Installation

A database or any other external dependency is not required for this test.

composer install

Example

<?php

use Lendable\Interview\Interpolation\Model\LoanApplication;
use Lendable\Interview\Interpolation\Service\Fee\FeeCalculator;

$calculator = new FeeCalculator();

$application = new LoanApplication(24, 2750);
$fee = $calculator->calculate($application);
// $fee = (float) 115.0

Fee Structure

The fee structure doesn't follow particular algorithm and it is possible that same fee will be applicable for different amounts.

Term 12

£1000: £50
£2000: £90
£3000: £90
£4000: £115
£5000: £100
£6000: £120
£7000: £140
£8000: £160
£9000: £180
£10000: £200
£11000: £220
£12000: £240
£13000: £260
£14000: £280
£15000: £300
£16000: £320
£17000: £340
£18000: £360
£19000: £380
£20000: £400

Term 24