If y varies directly as x and z, and y = 40 when x = 5 andz = 4, find y when x = 2 andz = 1.
a. y =12xz; }(2, 1) = 24
y = -xz; y(2, 1) =1
b. y =2xz; y(2, 1) -4
d. y=-xz; y(2, 1) =
select the best answer from the choices provided