How to distribute salary and elements across multiple assignments of an employee based on FTE

Our client has employees with multiple assignments. Now when a salary is assigned or an element entry is created for an employee, the client wants the values to be divided across multiple assignments as per the total FTE distribution across the assignments.

Eg.

Employee1 has three assignments i.e. Asg1(FTE 0.5), Asg2(FTE 0.5), and Asg3(FTE 0.4). When I assign a salary basis (eg. Annual Salary Basis $1400/month) and create an element entry (eg. Car Allowance with the value of $100/month) The monthly distribution should be like this:

How to achieve this? Note: The customer has opted for ORC, Oracle Compensation, and Core HR, they don't have Oracle Payroll.