Calculate the EMF of a current source with an internal resistance of 1 Ohm, if you know that when you connect a resistor

Calculate the EMF of a current source with an internal resistance of 1 Ohm, if you know that when you connect a resistor with an unknown resistance to it, the ammeter shows 2 A, and the ideal voltmeter shows 8V.

Given:
R = 1 ohm;
I = 2 A;
B = 8 B.
Find: EMF source.
Decision:
In order to find the EMF of the source, you need only one formula:
EMF = B + I * r.
Since we know all the values in it, we can substitute them into the formula and find the answer:
EMF = 8 + 1 * 2 = 10 V
Answer: 10