Two large containers X and Y of the same size are filled with different fluids. The fluids in containers X and Y are maintained at 0° C and 10° C, respectively. A small metal bar, whose initial temperature is 81° C, is lowered into container X. After 1.5 minute the temperature of the bar is 90° C. After 3 minutes the bar is removed and instantly transferred to the other container. After 2.5 minute in container Y the temperature of the bar decreases 15°. How long, measured from the start of the entire process, will it take the bar to reach 9.9° C?

Two large containers X and Y of the same size are filled with different fluids. The fluids in containers X and Y are maintained at 0° C and 10° C, respectively. A small metal bar, whose initial temperature is 81° C, is lowered into container X. After 1.5 minute the temperature of the bar is 90° C. After 3 minutes the bar is removed and instantly transferred to the other container. After 2.5 minute in container Y the temperature of the bar decreases 15°. How long, measured from the start of the entire process, will it take the bar to reach 9.9° C?