What does PTO indicate ?​

Paid time off is referred to as PTO. Businesses may use this term in place of vacation time, sick leave, personal leave, or other words to describe their policies about paid time off for employees.

Historians are researchers of the past or people who understand the history of people. with this field, they must possess qualities such as being unbiased, patient, efficient reader, has a knack for logic and critical thinking and reasoning, disciplined, open-minded, resourceful, with good analytical ability, good reasoning skills and problem solving!

Well, a and b together would be negative. b alone would also be negative.