50 000 x 10 = 500 000n (since we like this to be in newton)

 

now the drag, we have a Lift/Drag ratio of 10 that is (1/10)

 

and we only talk about a small climb angle this equals 500 000/10 = 50 000n

 

Thrust = 80 000 (20 000n x 4 engines)

 

Climb gradient = (Thrust -drag)/ weight X100

 

this gives us the following:

 

((80 000 - 50 000) / 500 000 ) x 100 = 6

 

my answer 6%