Answer:
1) The maximum jump height is reached at A. 
2) The maximum center of mass height off of the ground is B. 
3) The time of flight is C. 
4) The distance of jump is B. 
Explanation:
First of all we need to decompose velocity in its rectangular components, so

1) We use,
, as we clear it for
and using the fact that
at max height, we obtain 
2) We can use the formula
for
, so

3) We can use the formula
, to find total time of fligth, so
, as it is a second-grade polynomial, we find that its positive root is
4) Finally, we use
, as it has an additional displacement of
due the leg extension we obtain,
, aprox 