Excel 2010: Formula to work out Salaries per financial year per area

Code:

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Office        Employee        Start Date        Exit Date        Basic per Month
Office1        Person1        01/01/2014        01/11/2014        10000
Office1        Person2        01/02/2015        01/05/2018        10000
Office2        Person3        01/06/2016        01/07/2018        10000
Office3        Person4        01/01/2014        01/12/2018        10000
Office3        Person5        01/01/2014        01/12/2018        10000

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Code:

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2014                Office1        Office2        Office3
Salaries

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I need a formula in the 2nd table to calculate salaries by Office and Year (2014 in the above example, but this is a dropdown so can be 2015 or 2016 etc) for the year selected based on the start and exit dates and the monthly basic in the table above,

Any guidance appreciated!

see the attached file.