Is buying in installments through the Armed Forces Service apparatus, where the installment is deducted directly from the officer's pension without his intervention, permissible or forbidden?

The question has three possibilities:

1. The service and exhibition department is a single entity that owns the goods. In this case, selling them in installments to the officer is permissible. 2. The service department is separate from the exhibitions, and it has three scenarios: a. The department's role is solely financing: it pays the price to the exhibitions and then takes it from the officer's salary. If it takes it with an increase, it is a prohibited usurious loan. b. The service department buys the commodity from the exhibitions and then sells it to the officer. In this case, the department must take possession of the commodity and remove it from the exhibitions before selling it. c. The department's role is limited to collecting the price from the officer's salary and then delivering it to the exhibitions. This is permissible and constitutes an agency and guarantee contract.