Determine efficiency, voltage, current from motor characteristic curves

I would to identify efficiency, voltage, current for a particular Brush less DC motor in our lab given characteristic curves.

Electrical specifications are

The operating conditions are

Torque: 0.35 N.m
RPM   : 1200

Based on the operating condition, i drawed one more torque vs speed line (orange color) passing through 0.35 N.m & 1200 rpm and keeping slope constant.

To explain the image

Horizontal axis (X) : Torque (N.m)
Left Vertical axis  : U(V)     - Applied voltage         - Light Blue color

                      I(A)     - Current                 - Green color
                      P1(w)    - Electrical power input  - Dark Blue color
Right Vertical axis : n(r/min) - Revolution per min      - Orange color
                      P2(w)    - Mechanical power output - Red color
                      Eff(%)   - Efficiency              - Brown color

Unfortunately, i don't have better quality image. Please click on the image or Zoom the browser page to enlarge a bit more.

I have drawn few vertical and horizontal dashed lines(pink in color) passing through the operating point (0.35 N.m and 1200 rpm).

Question:

As the voltage vary the torque vs speed curves, does the efficiency curve vary ? what about the voltage and current ?

What are the approximate values in my case ?

Current = 8 Amps ?
Voltage = 15.00 or 17.50 V ?
Efficiency = 50 % ?

Thanks