Please help, due tomorrow. will give brainlist given f(x)=x^3-4x+k, and the remainder when f(x) is divided by x-5 is 91, then what is the value of k?

Technicians have installed a center pivot, circular irrigator for a farm that covers 25 acres. a.) how long is the irrigation boom (in feet) from the center pivot to its farthest extent? b.) if the irrigation boom makes 4 full revolutions in a day, how many miles does the end of the boom travel in 5 days?