During the 10 year period from 2007 through 2016 the total number of smartphones sold worldwide increased exponentially. At the end of 2008 (the second year of data) the total number of phones sold was 262.61 million and the total was 1,202.64 million at the end of 2011 (the fifth year of data). (a) Determine a model for the total number of smartphones sold worldwide as a function of time. (b) Use your model to determine when the total number of smart- phones sold will reach 1 billion. (c) Use your model to predict the total number of smartphones sold in 2016, in 2199 and in 1899. Do these numbers seem reasonable? Explain why or why not. What assumptions have you made in creating your model that affect its reasonableness? (d) A global telecom company can handle 4 billion smartphones on its network, but will need to upgrade for larger numbers of users. They have asked you to use your model to predict when those upgrades will be necessary. What answer will you give them and what warnings will you include about your prediction?