[填空题]
Two children are playing on two trymw1mfe(qm 2./xirij((kxaw 7 p.o.w ampod t v1mh72fkruyy4m2t49h d( mlines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chivkmhy1 mrmd2 uhty(d94f7t24 ld is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$ m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$ m/s(retain one decimal places)
(c) How long was the first child in the air? s