The exchange rate is 350 turns for $1. For every $5 in a single donation, you will receive a $3 turns bonus.

Which equals 2,800 turns for $5 donation since you are given a $3 bonus on top of that.

The exchange rate is 300 CP for $1. For every $5 in a single donation, you will receive a $3 CP bonus.

Which equals 2,400 CP for $5 donation since you are given the $3 bonus on top of that.