प्रयागराज एक्सप्रेस - जो भी हो तुम खुदा की कसम; लाजवाब हो

Why dont you do some homework of the route and put your comment. Mail is speeded up 4-5 hrs but after speedup both take equal time from Mumbai CST to Guntakal 14 45hrs while the fastest train train 13.5hrs. if Guntakal to YNK is fully doubled then it will reach in 5hrs and another hr to SBC total it can decrease to max of 19.5-20hrs that too if it's given first pirority. 18 hrs is not possible which you have put in 1st comment and 20hrs in last comment looks realistic.