My friend gave me this equation and I am curious/ need help in how to solve it.

"If a roll of a certain kind of wrapping paper is unrolled, the wrapping paper forms a rectangle that is 3ft by 20ft long. The wrapping paper is to be covered with an array of ladybugs by repeating the design (shown: 3inch = 4 lady bugs & 2 inch = 3 lady bugs). how many ladybugs will be on the wrapping paper?"

He says the answer is, 17280.

Nevertheless, I know 3ft = 36in & 20ft = 240 in. Also, the bugs seem to increase 1 bug per inch. So, how can I reach the correct answer?