(a)  The value of R_1 and R_2 isThe value of zero-adjust resistor R2 =100.0 ohm
The value of current-limiting resistor R1 =1966.7 ohm

(b)  The maximum value of R2 to compensate the drop in battery voltage = 143 ohm
The true value of the half-scale mark on the meter is = 2003.713 ohm

(c)  The percentage error = -0.185%
 
 The negative sign indicates that the meter reading is low