Probability of selecting 3 non-Ace and 1 Ace out of 52 cards is equal to 48C3×4C152C4
Since we want 4th card to be first ace, we will also have to consider the arrangement, Now 4 cards in sample space can be arranged in 4! ways and, favorable they can be arranged in 3! ways as we want 4th position to be occupied by ace
Hence required probability=48C3×4C152C4×3!4!