To solve this problem you must apply the proccedure shown below:
1. You have the following information given in the problem above: the velocity of the plane is represented by v=30i-492j+42k.
2. Therefore, you have that you can calculate the magnitude as below:
v= √(A^2 + B^2 + C^2)
v=√(30^2+492^2+42^2)
3. Then, you have that the result is:
v=494.7 mph
The answer is: b. 494.7 mph