Can you please give a simple and clear solution. Thank you

a. In a transmission, digital data of 110110101 will be transmitted. CRC algorithm will be used for error detection. By using generating polynom G(x) = x4 + x + 1, FCS (error control) bits are calculated and added to above data. Although some of data bits are changed during signal transmission receiver could not detect the error. In this situation, at least how many bits might be changed? Why? Give an example. (15 p) For error detection 2D Parity is used. During the transmission if underscored bits are changed, can the receiver detect the error with row parities? (10 p) b