Refer to figures.
Drift
Drift angle is how many degrees the heading (HDG) is to the right or left of the track (TRK). For example, a drift of 5° right means that our heading (HDG) is 5° to the left of the track, to counteract the incoming wind from the left.

CALCULATION OF HEADING
We can use a flight computer (CRP-5) to calculate the HDG using the following steps:
Steps 1 - 3 (Figure 1)

1. Set the center to your True Airspeed (TAS) of 90 kt.
2. Bring wind direction of 290° under the “TRUE HEADING”.
3. Mark a dot at the wind speed of 15 kt BELOW the center, at 75 kt.

Steps 4 - 7 (Figure 2)

4. Bring true track of 320° under the “TRUE HEADING”.
5. This value will result in a drift of 6°R (+).
6. Decrease value under the “TRUE HEADING” by 6° so that the difference between HDG and drift results in a TRK of 320°.
7. Read the True HDG of 314° under the “TRUE HEADING".

Therefore, the closest answer is: Heading = 315°(T)