Represent the following sentence by a Boolean equation.

The company safe can be unlocked only when Mr$.$ Jones is in the office or Mr$.$ Evans is in the office, and only within working hours, and only when the security guard is present.

U $=($J $+$ E$)($B $+$ S$).$ U: Safe unlocked, J: Mr$.$ Jones present, E: Mr$.$ Evans present, B: Normal business hours, S: Security guard present.

U $=$ JE $+$ BS$.$ U: Safe unlocked, J: Mr$.$ Jones present, E: Mr$.$ Evans present, B: Normal business hours, S: Security guard present.

U $=$ JE $+$ B $+$ S$.$ U: Safe unlocked, J: Mr$.$ Jones present, E: Mr$.$ Evans present, B: Normal business hours, S: Security guard present.

U $=($J $+$ E$)$BS$.$ U: Safe unlocked, J: Mr$.$ Jones present, E: Mr$.$ Evans present, B: Normal business hours, S: Security guard present.