The ans is A. 355 m/s as temperature is above stp
The efficiency of a machine is the ratio between the output power and the power in input:

in our problem, the output power is 3760 W while the input power is 4000 W, so the efficiency is

So the efficiency of the machine is 94%.
Answer:

°
Explanation:
Let's use the component method of vector addition:

Now, we know:

So:

Now lets calculate the magnitude of the vector B:

Finally its angle is given by:
°
Keep in mind that I added 180 to the angles of C and B to find the real angles measured from the + x axis counter-clock wise.