Aircraft
structures are designed to withstand a specified load with a very small safety
margin.
That safety
margin is 1.5.
The question
states that the aircraft is stressed to -1.9 to + 3.8g.
The turbulence
has stressed the aircraft to +4.2g.
This exceeds
the limit of 3.8 but has not exceeded the ultimate limit (3.8 x 1.5 = 5.7g)
The structure
will therefore not fail but be permanently damaged.