The voltage V in volts produced by a battery is a linear function of the i in amperes drawn from it .The opposite of the slope of the line repesents the battery 's effective resistance R in ohms .For a certain battery ,
V=12.0 when i = 10.0
and V=8.4 when i=10.0
a) What is the effective resistance of the battery ?
b) Find the voltage that the battery would producfe when the current is 25.0 amperes
The key for: a=0.4o hm
b = 2.4 volts

I know a)=
(12-8.4)/(1.0-10.0)
(3.6)/(9) =0.4 ohm
I can't fig b)

Question

The voltage V in volts produced by a battery is a linear function of the i in amperes drawn from it .The opposite of the slope of  the line  repesents the battery 's effective resistance R in ohms .For a certain battery , 
V=12.0 when i = 10.0  
and V=8.4 when i=10.0 
a) What is the effective resistance of the battery ? 
b) Find the voltage that the battery would producfe when the current is 25.0 amperes
The key for:   a=0.4o hm
                      b = 2.4 volts

I  know   a)= 
(12-8.4)/(1.0-10.0)
 (3.6)/(9) =0.4 ohm 
I can't fig b)