Interpreting and Applying Disclosures on Property and Equipment
Following are selected disclosures from the 10-K report of Facebook Inc. Facebook reported 2018 sales of $55,838 million.        
Property and Equipment, Net    
   December 31, $ millions
                                                   2018                           2017

Land                                         $899                           $798                                                                
Buildings                                  7,401                         4,909  
Leasehold improvements     1,841                            959    

Network equipment               13,017                      7,998    
Computer software, office equipment, and other    1,187               681  
Construction in progress       7,228                         2,992    
Total                                          31,573                    18,337
Less: Accumulated depreciation -6,890 -4,616  

Property and equipment, net $24,683  $13,721      

Depreciation expense on property and equipment was $3.68 billion and $2.33 billion during 2018 and 2017, respectively.                                                                                                                                                                         (a) Compute the PPE turnover for 2018.
Round answer to one decimal place.                            

(b) Estimate the useful life, on average, for its depreciable PPE assets.    
         Round your answer to one decimal place.            
                                    years            5.2
  (c) By what percentage are Facebook's assets "used up" at year-end 2018?          
    Round your answer to one decimal place.            
                                 36.3   %