Which two of the following could be considered as 'cost drivers' in Yip's 'drivers of internationalisation' model?
a. An international agency gains from economies of scale.
b. An agency has global customers.
c. Advertising regulations are being standardised across different regional markets.
d. An agency is able to exploit cheaper labour in one of its locations, e.g. WRSX can employ new media expertise in Singapore at lower wage rates.