Answer:
Journal entries
Feb 01 
Rent Expense                                           Debit               $ 200
Cash                                                          Credit                                   $ 200
Record payment of hanger rent for Feb
Feb 04
Cash                                                          Debit              $ 800
Unearned Revenue                                  Credit                                  $ 800
Recording of cash received in advance
Feb 7
Cash                                                           Debit             $ 900
Service Revenue                                       Credit                                $ 900
To record service revenue received in cash
Feb 10
Salaries and wages                                  Debit           $ 1,200
Cash                                                          Credit                                $ 1,200
To record salaries paid for services received in February
Feb 14
Advertisement expenses                         Debit          $    100
Cash                                                          Credit                               $    100
To record payment of advertisement expenses
Feb 18
Cash                                                          Debit            $ 500
Accounts Receivables                              Debit         $ 1,200
Service Revenue                                       Credit                             $ 1,700
To record services provided on cash and on credit
Feb 25
Supplies Inventory                                   Debit           $ 1,350
Accounts Payable                                    Credit                              $ 1,350
Recording of purchase of supplies for future use on credit
The preliminary net income for February is $ 1,100
The net profit margin is  42.3 %
Explanation:
Computation of net income and net profit margin
Revenues   ( $   900 + $ 1,700 )                                                     $ 2,600      
Expenses ($ 200 + $ 1,200 + $ 100 )                                             <u>$ 1,500</u>
Net Income                                                                                      $ 1,100    
Net profit margin = Net income / Revenues
Net Profit margin   = $ 1,100/ $ 2,600 =                                          42.3 %  
The other entries for collections made on Feb 04 for services to be performed next month and the purchase of supplies to be used in the future are not to be considered in revenues and expenses as they do not pertain to the current month