It takes six minutes for just the cold tap to fill my bath with water.

The hot tap fills the bath at the same rate, but unfortunately (due to some strange plumbing) after the hot tap has been running for three minutes its supply of water shuts off for a full two and a half while the hot water tank refills and reheats - after the two and a half minutes, the hot tap commences dispensing water once again.

With the plug pulled out, a full bath empties (at a uniform rate) in only four minutes.

With the hot water tank full and the plug pulled out, how long will it take my bath to fill if I turn both taps on?