When finding out error in this block matrix, the first error when checking column wise is in d2, right? So, the error in d2 in turn causes error at d3 too, since the 1 carry from d2 is omitted the d3 result is also wrong.
So, while calculating errors, don't we have to calculate the propogated errors? Bcoz if we count that then total number of errors is more than the highest number given in the options.
