FT Question

[benbret]

NFHS Rules
With about 1:30 left in the game B25 fouls A10. R1 reports the foul and the scorer tells R1 that is the fifth foul on B25. R1 tells B25 that is his 5th foul. R1 then tells the Coach of Team B that B25 has 5 fouls. B25 then goes to to bench. R1 tells the clock keeper to start the 15 second timer. Before B Coach has an opportunity to replace B25, R2 lets A10 shoot the first FT and it is good. B coach then tells R1 that A10 can not shoot the free throw until he has replace B25. He says that they cannot play with just 4 players. Should R allow B coach to replace B25 and not allow the first FT or should the FT count? Is there a rule for this situation?