Which value for the constant c makes z = -5/4 an extraneous solution in the following equation?

(start of square root) 4z + 9 (end of square root) = cz + 8

Aschool allots ? 1500 to spend on a trip to the theatre. theatre tickets have a regular cost of ? 55 each and are on offer for 1 5 off. a train ticket for the day will cost ? 12 each. if 2 teachers and the maximum number of students attend, how much money will the school have left over?