How many parameters in a Conv2d Layer? I was following andrew-ng coursera course on deep learning and there's a question that has been asked there which I couldn't figure out the answer for?

Suppose your input is a 300 by 300 color (RGB) image, and you use a convolutional layer with 100 filters that are each 5x5. How many parameters does this hidden layer have (including the bias parameters)?


2501
2600
7500
7600
The right answer is the fourth. 

From this, the formula to calculate the number of parameters in a convolutional layer is (nml+1)*k with n = m = 5, k = 100, l = 3 and +1 for the bias.