A library charges a late fee of $0.25 for each day or partial day a book is overdue. What is the fee for a book that is 4.2 days overdue?

Each day or partial day counts as a full day, so $4.2$ days is billed as $5$ days. The fee is $5\cdot0.25=1.25$ dollars, choice H. Choice F ($1.05) multiplies the rate by the exact $4.2$ days, which ignores the rounding rule. Choice G ($1.20) bills $4.8$ days, a wrong amount. Choice J ($1.50) bills $6$ days. This kind of pricing is a step function, and any fraction of a day moves the bill up to the next whole day.