When you get your oil changed (assume "light oil" with specific heat 0.43 BTU/(lbm R) and density 56.8 lbm/ft$^3$), the mechanic adds your dirty and hot 4 quarts of oil to the recycling drum. If your oil is 200 $^\circ$F, and the drum already contains 4 gallons of oil at room temperature (80 $^\circ$F), then:

(a) What is the final temperature in the recycling drum? $^\circ$F

(b) What is the total change in entropy? $\displaystyle \frac{\text{Btu}}{\text{R}}$