The difference between the ages of two sisters is the same as that of their father and mother. The elder sister is 24 years old. At the time of birth of the younger sister, their mother’s age was 30 years. If their father is 4 years elder to their mother, what was his age at the time of elder daughter's birth?

• A. 35 years
• B. 24 years
• C. 30 years
• D. 32 years