Kiara, an art lover, used to model different toys for children using colourful clay. She knew that along with her full-time job, she could model 30 toys on a working day and 45 toys on a weekend. From experience, she also knew that a standard box of clay, comprising a fixed quantity of clay (in kg) cost Rs. 3 more in the local stationary shop compared to the wholesale market in the city. Buying from the local stationary shop would also mean that she would get 2 kg less clay per rupee. At the start of a particular week, Kiara bought 20 standard boxes of clay from the wholesale market. This week had five working days. She worked throughout the week and managed to completely use the clay content from each box to just complete making all the toys. She sold all the toys for Rs. 1,800. If each toy weighed the same i.e. a kg, what was Kiara’s profit margin per toy?