Machine m, working alone at its constant rate, produces x widgets every 4 minutes. machine n, working alone at its constant rate, produces y widgets every 5 minutes. if machines m and n work simultaneously at their respective constant rates for 20 minutes, does machine m produce more widgets than machine n at that time?

Yes

Explanation:

In 4 minutes, machine M produces x widgets

In 20 minutes, machine M produces 5x widgets

Assuming x = 1, in 20 minutes machine M produces 5 widgets

In 5 minutes, machine N produces y widgets

In 20 minutes, machine N produces 4y widgets

Assuming y = 1, in 20 minutes machine N produces 4 widgets

Machine M produces 1 more widget than machine N in 20 minutes assuming x=1 and y=1

d. platinum would have the greatest temperature increase because it has the lowest specific heat.