Dissolution of Partnership vs Discontinuation of Business

As per sec 176(3) , AO should be informed within 15 days of Discontinuation of Business otherwise penalty u/s 272A(2) (b) is Rs. 500/- per day  default continues. Now M/s XYZ is a Partneship Firm of which A and B were Two partners. A retires and automatically partnership dissolved and in Deed of dissolution ,it is written that after retirement of Partner A , M/s XYZ will be reconstituted as Soleproprietorship firm of which B is sole proprietor. Now my question is whether Dissolution of Partnership will be considered same as Discontinuation of Business of Partnership Firm and penalty u/s 272A(2)(b) is applicale if AO is not informed within 15 days about such Dissolution of Partnership Firm or It is just dissolution of Firm  and business remains to continue as sole proprietorship firm , so intimation u/s 176(3) and corresponding penalty for any default u/s 272A(2)(b) is not applicable in such case? Which one is correct pls suggest.