Final answer:
The calculation of Sandra's CPP retirement pension is a math-related task that requires specific formulas used by the CPP, which are not provided. The number of months for retroactive payments depends on the application date, and her PRB for 2022 would be based on the contributions from her income in 2021.
Step-by-step explanation:
As the question about the calculation of Sandra's Canada Pension Plan (CPP) retirement pension involves understanding and applying financial formulas and concepts, it's primarily a mathematics question at the high school level. Without the specific formulas and percentages used by the Canada Pension Plan to calculate retirement pensions, it's not possible to provide an exact amount for Sandra's CPP retirement pension. Generally, the CPP retirement pension is calculated based on a formula that takes into account the years of contribution and the amount contributed over a person's working life. Sandra's PRB (Pensionable Retirement Benefit) for 2022 following her return to work would depend on the CPP contributions made on her $30,000 income in 2021.
As for the retroactive payments, Sandra would typically be paid retroactive benefits for up to 11 months if she applied after she turned 65, but the specific number of months would depend on the date she applied for her CPP retirement pension relative to her 65th birthday.