Amount C arises if paragraph (c) of section 179(2) (amount payable for a period to be not less than required amount) is not complied with and is calculated as follows.

In relation to each period beginning with the date on which the loan is made and ending with the last day of a loan year, calculate—

$\mathrm{RA}-\mathrm{AP}$

where—

RA is the required amount in relation to that period, and

AP is the amount payable during that period.

If an amount calculated under sub-paragraph (2) is negative, treat that amount as nil.

Amount C is the largest of the amounts calculated under sub-paragraph (2).