I need to drive from A to C via B at total distance of L$.$ The distance from A to B is $\backslash$Delta L$1,$ from B to C is $\backslash$Delta L$2.$ I have time t to get from A to C$,$ so I figure I can make it if I average $=$ L$/$t for the entire trip. Going from A to B the traffic is heavy and I can only average a speed v$1.$ How fast do I have to go from B to C in order to average for the whole trip? Write an equation expressing v$2($the speed I need to average going from B to C$)$ in terms of the other symbols given: L$1,$ L$2,$ v$1,$ and t$.($Why these particular variables?$)$