A sample containing Au+ ions were tested using a gold ISE. The response of the electrode is E=K⁺0.0592Vlog[Au+]. Into each 50.00 test solution was placed 25.00mL of sample, 10mL of buffer, and ______ mL of ________.
1) 15mL, water
2) 20mL, solution
3) 25mL, buffer
4) 30mL, sample