To calculate the gross pay of the per diem employee, we need to multiply his daily rate by the number of days he worked in the month.
Daily pay = $110.00
Number of days worked = 25
Gross pay = Daily pay x Number of days worked
Gross pay = $110.00 x 25
Gross pay = $2,750.00
Therefore, the gross pay of the per diem employee is $2,750.00.