Please can someone help with part d only, thank you.(the answers for part a, b, c, are provided.

The air in a 46 cubic metre kitchen is initially clean, but when Sally burns his toast while making breakfast, smoke is mixed with the room's air at a rate of 0.04 mg per second. An air conditioning system exchanges the mixture of air and smoke with clean air at a rate of 6 cubic metres per minute. Assume that the pollutants are mixed uniformly throughout the room and that burnt toast is taken outside after 55 seconds. Let S(t) be the amount of smoke in mg in the room at time t (in seconds) after the toast first began to burn.

1. The differential equation is dS(t)dt= 0.04-S(t)/460
2. As a check that your solution is correct, test one value. S(13)= 0.5127209063 mg
3. Check the level of pollution after 55 seconds by entering your answer here, correct to 10 significant figures (do not include the units): 0.04507754474 mg m3
4. The time, in seconds, when the level of pollution falls to 0.002 mg per cubic metre is ??? seconds. Note that this check asks for the time since t=0 but the question part (d) asks for a time since the toast was taken outside.