What are the shares for a wife, mother, sister, and paternal grandfather?

Primary text

When a deceased leaves behind a wife, mother, sister, and paternal grandfather, the wife inherits one-fourth (1/4), and the mother inherits one-third (1/3). The remainder is divided between the grandfather and the sister according to a ratio of three parts, making the original denominator twelve. The distribution is sound if the total is calculated from thirty-six.