CP of the chair which is sold at 25% of profit = Rs 4000/ (1+ 25%)
= Rs 4000/1.25
= Rs 3200
Now given, that sum of CP pf table and chair= sum of SP of table and Chair
⇒ 8000= 3200 + CP of Table
⇒ CP of Table = Rs 4800
⇒ Loss on Cost price of table = Rs 4800- Rs 4000= Rs 8000
⇒ Loss % = 8000/4800 = 16.66%