just problem 2, pls don't do the example problem

2. What happens in Example 1 if we replace T1 by a tank containing 200 gal of water and 150lb of fertilizer dissolved in it? EXAMPLE 1 Mixing Problem Involving Two Tanks A mixing problem involving a single tank is modeled by a single ODE, and you may first review the corresponding Example 3 in Sec. 1.3 because the principle of modeling will be the same for two tanks. The model will be a system of two first-order ODEs. Tank T1 and T2 in Fig. 78 contain initially 100gal of water each. In T1 the water is pure, whereas 150lb of fertilizer are dissolved in T2. By circulating liquid at a rate of 2gal/min and stirring (to keep the mixture uniform) the amounts of fertilizer y1(t) in T1 and y2(t) in T2 change with time t. How long should we let the liquid circulate so that T1 will contain at least half as much fertilizer as there will be left in T2 ? SEC. 4.1 Systems of ODEs as Models in Engineering Applications 131