Answer:
1.21'
Step-by-step explanation:
Volume = (6-2x)(10-2x)(x)
= (60-12x-20x+4x²)(x)
= 4x³-32x²+60x
dV/dx = 12x² - 64x + 60 = 0
3x² - 16x + 15 = 0
x = 4.1196 , 1.2137
d²V/dx² = 6x - 16
at x = 4.1196, +ve
at x = 1.2136, -ve
x should be small for max volume,
So x = 1.21' (3 sf)