ðˈʌs, wiː hæv sˈɑːlvd ðɪs pɹˈɑːbləm jˈuːzɪŋ ˈoʊnli kˈuːlɑːmz lˈɔː, ðə dˌɛfɪnˈɪʃən ʌv wˈɜːk, ænd ðə ɡɹˈeɪdiənt θˈiəɹəm.
Thus, we have solved this problem using only Coulomb's Law, the definition of work, and the gradient theorem.