calculation of open circuit voltage and short circuit current in DC welding

Question

In a DC arc welding operation, the length characteristic was obtained as V_arc = 20 +5l where the are length l was varied between 5mm and 7mm. Here V_arc denoted the arc voltage in Volts. The arc current was varied from 400A to 500A. assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation  are

(a) 45V, 450A                            (b) 75V, 750A

(c) 95V, 950A                           (d) 150V, 1500A