the bridge won’t collapse cause the truck has crossed half the bridge and in doing so has consumed some amount of fuel which is subtracted from the weight of the truck hence the weight of the bird will not affect as it wouldn’t be greater than the weight of fuel consumed by the truck.

Answer is 2
Logic :
40*14=560=5+6+0=11
30*13=390=3+9+0=12
20*12=240=2+4+0=6
So 10*11=110=1+1+0=2