A = delta v over delta t delta v is calculated with final velocity less initial velocity then delta v is equals to 20 - 0 that is 20m/s and to calculate delta t is like delta v is final time less initial time as initial time always is 0 the delta t is equals to 10s then a = 20/10 then acceleration is 10m/s^2 (remember that is squared)
4 because it’s is the highest one hope it helps