Incorrect ATM Interest calculation in certain conditions

[Ierdna100]

The ATM interest calculation does not correctly work if more than 1 day has passed since the user loaded Open Sewer Tenement.

The current calculation does
$\text{Sum} = 1 + \text{Days Since Last Calculation} \cdot \text{Interest}$

Which does not account for money accumulating over time like in the real interest calculation, which should be:
$\text{Sum} = (1 + \text{Interest}) ^ \text{Days Since Last Calculation}$