The level of liquid in a processing tank, L L\,L units, varies over a long cycle given by the formula: L=12−6sin(15t)L = 12 - 6\sin(15t)L=12−6sin(15t), where t t\,t is the time in hours since the start of the week.
a.[4]
On the axes below, draw the graph of L L\,L against t t\,t for 0≤t≤240 \leq t \leq 240≤t≤24
b.[2]
Find the two values of ttt, where 0≤t≤480 \leq t \leq 480≤t≤48, when the liquid level is least.