F.4 app. of differentiation

1)
http://img526.imageshack.us/img526/7091/dsc00569u.jpg
http://img517.imageshack.us/img517/5653/dsc00572y.jpg
ans: ai)y=x/2 aii)0.25m/s
bi) z=3x/2 bii) 0.75m/s away from the lamppost

2)
http://img268.imageshack.us/img268/6221/dsc00573hur.jpg
a)8m/h b)512pie m^3/h c)32006pie/3 m^3


3)
http://img195.imageshack.us/img195/5052/dsc00575ni.jpg
Ist question: a)0.3226 b)29.6739 c)1.7752/h
2 nd question: 10root3 b)root3/40 cm /min



pls show clear steps.thx a lot!