HI all,

I am getting the following error, can anyone give me a hint why the shape is not right?

```
ValueError Traceback (most recent call last)
<ipython-input-55-182241fd5e53> in <module>
6 "stride": 2}
7
----> 8 Z, cache_conv = conv_forward(A_prev, W, b, hparameters)
9 print("Z's mean =\n", np.mean(Z))
10 print("Z[0,2,1] =\n", Z[0, 2, 1])
<ipython-input-54-c0893c722a68> in conv_forward(A_prev, W, b, hparameters)
96 weights = W[:,:,:,c]
97 biases = b[:,:,:,c]
---> 98 Z[i, h, w, c] = conv_single_step(a_slice_prev, weights, biases)
99
100
<ipython-input-24-2e7aa7881504> in conv_single_step(a_slice_prev, W, b)
24 # YOUR CODE STARTS HERE
25
---> 26 s = np.multiply(a_slice_prev, W)
27 Z = np.sum(s)
28 Z = Z + np.float(b)
ValueError: operands could not be broadcast together with shapes (3,2,4) (3,3,4)
```