Помогите, пожалуйста, выполнить упражнение по временамSimple Past / Present PerfectSince

Помогите, пожалуйста, выполнить упражнение по временам
Simple Past / Present Perfect
Since computers were first introduced to the public in the early 1980's, technology (change) a great deal. The first computers (be) simple machines designed for basic tasks. They (have, not) much memory and they (be, not) very powerful. Early computers were often quite expensive and customers often (pay) thousands of dollars for machines which actually (do) very little. Most computers (be) separate, individual machines used mostly as expensive typewriters or for playing games.

Times (change) . Computers (become) powerful machines with very practical applications. Programmers (create) a large selection of useful programs which do everything from teaching foreign languages to bookkeeping. We are still playing video games, but today's games (become) faster, more exciting interactive adventures. Many computer users (get, also) on the Internet and (begin) communicating with other computer users around the world. We (start) to create international communities online. In short, the simple, individual machines of the past (evolve) into an international World Wide Web of knowledge.