angular exercise at uni -- 3

Hi, I have a simple study exercise, which is written on one file - for intermediate Angular programmer - 30 mins of work. I would offer 10EUR. I am using Angular, FormGroup, FormArray and FormControls. The task is to create a nested FormGroups, where the number of nested FormGroups depends on user input number. The formControls should user Validator.required. When user fills in the form, simple calculator gets values and assigns them to object. Thats it! I have done all the job and i get errors. I have to use FormGroup inside FormArray. Your job would be: 1) remove the error and tell me what was wrong - when building dinamically formarray 2) implement one [login to view URL] and tell me why mine didn't work 3) Implement one assignment to object property after user submits and tell me what was wrong with mine. As I said, the code is written. I need your help to explain - what i am doing wrong and - to fix these 3 things.