Solution:
As, in a pack of cards, there are 26 black cards and 26 red cards.
Probability of an event =

Probability of drawing a black card from a pack of 52 cards =

As each card drawn is replaced,Each black card draw is an independent with another black card draw.
Probabilities of drawing a black card on each of four trial=
![(1)/(2)* (1)/(2)* (1)/(2)* (1)/(2)=[(1)/(2)]^4](https://img.qammunity.org/2017/formulas/mathematics/high-school/xui5x90eangi8hk08plqha7b9umsifd33n.png)