It is calculus 1 and it is about optimization, I need all work shown.

9 ) The velocity of a particle ( inft ) is given by vat'-5+ +6 , where I is the time (on second) for which it has traveled. Find the time at which the veluily is at a minimum. a) 35 b) Ss () 2.5 5 D) 6s 10) A rectangle sheet of perimeter 39 cm and dimensions & cm by y cm is to be milled into a cylinder as Shown in partial of the figure what values of t and y give the largest volume? circumference = * y X Q) x = 15 cm, y : 7 b)