Answer :

the highest height is when the 50t is the biggest in comparison to -16t^2
-16t^2+50t
if t=1 then -16 times 1^2+50(1)=34
if t=2 then -16 times 2^2+50(2)=36
if t=3 then =6
so therefor the max time is between 2 and 3 and the max height is about 36+10=46

it will take about 2 to 3 seconds, but more close to 2

for the time it reaches tthe ground, set h to zero
0=-16t^2+50t+10
put into quadratic formula
we get x=3.3136 or -0.1886
obviously it can't travel for - seconds so we discard

the answer is 3.3136 seconds

so
a. answer>46 by a little bit
b. answer>2 seconds by a little bit
c. 3.314 seconds